Objective: The 50th anniversary of the death of Theodor Ziehen was on December 29, 2000. As this occasion passed without fanfare, it is the authors' intent to recollect his importance in the field of child and adolescent psychiatry.
Methods: A short description of his life and an evaluation of his scientific work is presented based on earlier publications.
Results: Ziehen (1862-1950) was an extraordinarily versatile scholar. He is regarded as a great psychiatrist, psychologist and philosopher, as well as one of the founding fathers of child psychiatry. He began work on developmental psychiatry in Jena, publishing his first article "Association Psychology in Childhood" in 1898. He worked in close collaboration with the educators Rein and Trüper. In 1902 the first part of his book "Mental Diseases in Childhood" was published, followed by further publications in 1904 and 1906. These volumes are regarded as the second most important in child psychiatry in Germany. His work is the first systematic and almost complete compendium in this field. Ziehen introduced the medical terms "affective psychosis" and "psychopathic constitution" to psychiatric literature. He also worked in the fields of medical education and education.